Galatians 4:22
Because it is in the Writings, that Abraham had two sons, one by the servant-woman, and one by the free woman.
Genesis 16:15
And Hagar gave birth to a child, the son of Abram, to whom Abram gave the name of Ishmael.
Genesis 16:2-4
And Sarai said to Abram, See, the Lord has not let me have children; go in to my servant, for I may get a family through her. And Abram did as Sarai said.
Genesis 21:1-2
And the Lord came to Sarah as he had said and did to her as he had undertaken.
Genesis 21:10
So she said to Abraham, Send away that woman and her son: for the son of that woman is not to have a part in the heritage with my son Isaac.